SOME TURTLES LAY THEIR EGGS UNDER WATER

by Whit Gibbons


July 6, 2008


Professional ecologists are the major contributors to our knowledge of the natural history of plants, animals, and habitats. But scientists do not hold the franchise on discovering fascinating facts about the natural world. The origin for some important findings has been "professionally untrained" individuals.

The long-necked turtle of the Australian tropics is the only turtle in the world known to lay its eggs under water. Until an Australian biologist named Rod Kennett reported his research in the 1980s, scientists were not aware that any species of turtle did this. The operative word there is "scientists," because the egg-laying strategy of the long-necked turtle had actually been known for centuries.

Herpetologists have conducted research for decades on animals associated with billabongs, the lakes of Australia that alternate seasonally between wet and dry. Nonetheless, despite repeated searches by scientists, the nests of the long-necked turtle, a relatively common species, could not be found. Finally, after years of mystery and ignorance, Rod determined the unusual nesting behavior of the species through the use of radiotelemetry. He had already hypothesized that the turtles deposited their eggs in underwater nests.

He placed transmitters inside the oviducts of female long-necked turtles that were carrying eggs. Thus, the transmitter sending out a constant signal was deposited in the spot where the eggs were laid. By tracking the transmitters, Rod was able to locate the nesting sites, which were indeed beneath the water. He further discovered that the eggs hatch after the waters of the billabong recede during the dry season. Through detailed observations and persistence, science had again revealed a biological truth.

But the story of human knowledge of egg-laying by the long-necked turtle has a twist. I asked Rod why he ever suspected the nests were under water in the first place. The answer was straightforward enough: "Because the Aboriginal people in the region told me that the turtles nested under water." They had known the answer all along. But no one had asked, and they had never told anyone until Rod inquired.

A similar tale about northern Australia concerns another species, the pig-nosed turtle. Unique among freshwater turtle species of the world, this is the only living member in its family. Instead of having clawed feet like other freshwater turtles, pig-nosed turtles have flippers, like sea turtles. The first specimen was captured in a tributary to the Fly River in Papua New Guinea in 1886. Scientists did not expect the Fly River turtle, as it was then called, to occur on the southern continent of Australia. The freshwater turtle was assumed to be restricted to New Guinea, more than 150 ocean miles away. But in 1970 herpetologists reported that a population of the species was present in the Daly River in northern Australia. A recent introduction? No. And the turtle's presence was not a surprise to some, namely the Aboriginal people.

Aboriginal drawings on rock walls revealed that the original human inhabitants of Australia knew of the presence of pig-nosed turtles more than 7,000 years ago. Pig-nosed turtles had lived there for centuries, unsought by scientists because of their assumption that the turtles occurred only in New Guinea. The longtime inhabitants of the region knew the truth all along, but again, no one had asked them.

How many examples of this kind exist, in which so-called primitive peoples have knowledge that professionally trained scientists lack? Living coelacanths, ancient fishes assumed by scientists to have gone extinct millions of years ago, were familiar to native fishermen in the Indian Ocean long before their discovery by scientists in 1938. And the Boran people of Kenya told of the remarkable behavior of the greater honeyguide, a bird they said would lead forest hunters to bee hives. The natives of the region had been aware of this phenomenon for centuries, but modern scientists discounted the reports, until a scientific study published in 1989 demonstrated its validity.

The moral of this story (well, one of the morals) is that you do not have to be professionally trained to observe nature. So go on, look around you with a naive but discerning eye. It's possible you may see something no scientist has ever seen.




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